Official meteorological observations across Istanbul stations on September 11, 2026, recorded a daily maximum of 25°C under clear skies and moderate northeasterly flow, establishing the strong market consensus at that exact threshold. This aligns with seasonal norms for early autumn, where average highs hover near 25°C, and numerical weather models showed tight agreement without significant diurnal spikes or localized warming. The implied probability exceeding 99% reflects trader confidence in verified station data over broader forecasts. A revised official reading from a primary reference station or measurement protocol change could still alter resolution, though such adjustments remain rare once daily records close.